SOURCE PARAMETERS OF LARGE EARTHQUAKES IN THE EAST ANATOLIAN FAULT ZONE (TURKEY)

The East Anatolian Fault Zone accommodates most of the motion between the Arabian plate and the apparently little-deforming interior of central Turkey. The direction of overall slip across this zone is crucial to the determination of the slip rate on the North Anatolian Fault. We use long-period P- and SH-waveforms to determine the source parameters of the four largest earthquakes that occurred in, or near, the East Anatolian Fault Zone in the last 35 years. Only one of these actually involved left-lateral strike-slip motion on a NE-SW fault. But the other three, and the nearby 1975 Lice earthquake, all had steeply dipping nodal planes with a NNW strike: if these were the auxiliary planes then all the earthquakes had a slip vector direction within about 10-degrees of 063-degrees. If this direction represents the Arabia-Turkey motion, then the slip rate on the North Anatolian Fault must be in the range 31 to 48 mm yr-1, with a probable value of 38 mm yr-1, and the overall slip rate across the East Anatolian Fault Zone must be about 29 mm yr-1 with a range of 25-35 mm yr-1.